An Enhanced Gated Recurrent Unit-Based Adaptive Fault Diagnosis of Rotating Machinery

Table 1

The steps of signals denoising using WPD.

Steps	Detailed description
A. Signal decomposition	Select the wavelet function to decompose the noisy signals. Therefore, the wavelet packet coefficients at each level are obtained.
B. Thresholding	A threshold rule is used to decompose the coefficients to eliminate most of noisy coefficients
C. Signal reconstruction	The inverse WPD of each scale is performed by using the obtained approximate coefficients and the detailed coefficients of denoising.